+
+ start = (start - base) & (mod - 1);
+ goto use_start;
+ }
+
+ /*
+ * Typical case: reuse current schedule, stream is still active.
+ * Hopefully there are no gaps from the host falling behind
+ * (irq delays etc). If there are, the behavior depends on
+ * whether URB_ISO_ASAP is set.
+ */
+ start = (stream->next_uframe - base) & (mod - 1);
+ now2 = (now - base) & (mod - 1);
+
+ /* Is the schedule already full? */
+ if (unlikely(!empty && start < period)) {
+ ehci_dbg(ehci, "iso sched full %p (%u-%u < %u mod %u)\n",
+ urb, stream->next_uframe, base, period, mod);
+ status = -ENOSPC;
+ goto fail;
+ }
+
+ /* Is the next packet scheduled after the base time? */
+ if (likely(!empty || start <= now2 + period)) {
+
+ /* URB_ISO_ASAP: make sure that start >= next */
+ if (unlikely(start < next &&
+ (urb->transfer_flags & URB_ISO_ASAP)))
+ goto do_ASAP;
+
+ /* Otherwise use start, if it's not in the past */
+ if (likely(start >= now2))
+ goto use_start;
+
+ /* Otherwise we got an underrun while the queue was empty */
+ } else {
+ if (urb->transfer_flags & URB_ISO_ASAP)
+ goto do_ASAP;
+ wrap = mod;
+ now2 += mod;
+ }
+
+ /* How many uframes and packets do we need to skip? */
+ skip = (now2 - start + period - 1) & -period;
+ if (skip >= span) { /* Entirely in the past? */
+ ehci_dbg(ehci, "iso underrun %p (%u+%u < %u) [%u]\n",
+ urb, start + base, span - period, now2 + base,
+ base);
+
+ /* Try to keep the last TD intact for scanning later */
+ skip = span - period;
+
+ /* Will it come before the current scan position? */
+ if (empty) {
+ skip = span; /* Skip the entire URB */
+ status = 1; /* and give it back immediately */
+ iso_sched_free(stream, sched);
+ sched = NULL;
+ }